Prior to the present invention, various exhaust manifolds and methods of controlling exhaust gases have been disclosed In the prior art. U.S. Pat. No. 2,230,666 which issued on Feb. 4, 1941 and is entitled “Exhaust Gas Collector” discloses a plurality of laterally spaced exhaust pipes fluidly connected to the cylinders of an associated internal combustion engine open to a diverging funnel-like main exhaust tube providing reduced back pressure and thereby increasing the power of the engine. U.S. Pat. No. 4,288,988 which issued on Sep. 15, 1981 and is entitled “Method and Apparatus for Improving the Gas Flow in an Internal Combustion Engine Exhaust Manifold” discloses a method and apparatus for damping pressure oscillations in the exhaust manifold of an associated engine by throttling the exhaust gas near the outlet of the cylinders and then accelerating the gas flow in the manifold by providing a uniform flow section therein which is substantially smaller than the cylinder bore. U.S. Pat. No. 5,860,278 which issued on Jan. 19, 1999 and is entitled “Apparatus and Method for Providing a Compact Low Pressure Drop Exhaust Manifold” discloses a method and apparatus for Improving flow through the manifold and decreasing pressure drop to enhance engine performance.
While these and other prior manifold constructions control flow of engine exhaust gas as disclosed, one drawback is that such constructions can result in exhaust interference (i.e. a portion of the engine exhaust gas reflected back up the exhaust tube toward non-firing upstream engine cylinders) and reduced output depending on the exhaust order of the engine cylinders. It is therefore desirable to provide an exhaust manifold that is capable of reducing undesirable pneumatic interaction between cylinders and optimizing exhaust flow.
One solution in the art for reducing undesirable pneumatic interaction is contained In U.S. Pat. No. 7,171,805 to Ruehle which issued on Feb. 6, 2007 and is entitled “Deflector Style Exhaust Manifold”, wherein it is disclosed to provide an exhaust manifold is shown comprising a housing with a generally rectangular outer wall and providing a longitudinally extending main exhaust gas passage terminating in an outlet at one end and a plurality of discrete inlet branch passages arranged to provide separate gas passages in fluid communication with an associated exhaust valve of an engine. An initial inlet branch passage and an inner wall of the housing are arranged to provide a ninety degree angular change of flow direction as exhaust gas exits an exhaust port and enters the main exhaust gas passage. The remaining inlet branch passages are arranged to provide a deflector member between each inlet branch passage and the main exhaust gas passage which provides an angular change of flow direction requiring exhaust gas to enter the main exhaust gas passage in the downstream direction.
However, the space restrictions within the engine compartment of the modern motor vehicle may require that the main exhaust gas passage and the engine's exhaust ports are not co-planar with each other. More specifically, it may be necessary to arrange the exhaust manifold to place the main exhaust gas passage on a plane lower than the engine's exhaust ports. In such an arrangement, the mere provision of a deflector member between each inlet branch passage and the main exhaust gas passage is not sufficient to prevent undesirable pneumatic interaction between cylinders. This pneumatic interaction can be even further aggravated when the engine exhaust port has a relatively flat floor compared to an exhaust port with a floor having a high pitched curvature. In such systems, the amount of exhaust gas accumulating near the top of the main exhaust gas pressure is even more pronounced. It is therefore desirable to provide an exhaust manifold that permits the main exhaust gas passage and the engine's exhaust ports to be in non-coplanar fluid communication with each other while reducing undesirable pneumatic interaction between cylinders.